The coordinate expression of lysosomal enzymes will be studied in preimplantation mouse embryos. Specifically, we will characterize the acid hydrolases beta-glucuronidase alpha-galactosidase and beta-galactosidase. Genetic variants for each of these enzymes are being established in congenic C57BL/6 strains of mice. These strains will be used to determine how the developmental expression of these enzymes is regulated by variation at the structural gene locus.